1. Field of the Invention
The present invention relates to a box of the type having at least one base with high resistance to opening, and more particularly to a box with one or more closure bases or lids comprising cuts into which there extend hook-shaped teeth projecting from flaps below each base or lid, said teeth interfering with the base to substantially increase its resistance to opening.
2. Discussion of the Background
More particularly, the invention relates to a box of the aforesaid type, the base or lid of which becomes irredeemably broken, to prevent it from being reclosed after the base has been opened for the first time.
U.S. Pat. No. 4,890,789, the corresponding EP-B-0318750 and DE-A-3826231 describe boxes provided with at least one base or lid with high resistance to opening: this lid comprises a panel projecting from the box and having a projecting tab which can be folded and inserted into the interior of the box to the side of one or more flaps projecting from respective main lateral panels of the box and positioned below, i.e. on the inside, of the lid considered.
In and along the folding line which separates the lid panel from the tab there is provided a thin elongate window into which there become inserted (when the box is closed) two hooks or dovetail shaped teeth projecting one from each of the said flaps and superposed one above the other in the box when closed.
When the lid is pulled to open it, it drags and raises the said two teeth (which extend into said elongate window of the lid tab) away from their rest position: as the teeth are rigid with the flaps which are connected to the adjacent lateral panels of the box along folding lines inclined (generally perpendicular) to the folding line about which the lid can rotate, it follows that the raising of the two teeth (by the effect of the pull exerted on them by the lid to be opened) causes the teeth to move along two different circular arcs and to withdraw from each other within the window in which they are inserted, to hence strongly hook onto the tab in which this window is provided.
The result is that the resistance to opening of the box lid is strongly increased by the retention action exerted on it by the teeth projecting from the box flaps.
This does not prevent it being possible, using suitable care, to unhook the lid from the hook-shaped teeth of the flaps and open the box lid (or lids), to then reclose it such that its previous opening goes unnoticed.
U.S. Pat. No. 5,207,374, EP-B-0709293 and EP-A-1340684 describe boxes comprising a lid consisting of a closure panel from which there extends a foldable tab insertable into the box interior, in said tab there being provided two separate apertures which extend along the folding line separating the tab from the closure panel, below which two separate non-superposable flaps projecting from two lateral main walls of the box become positioned. From each flap there projects only one hook-shaped tooth which is inserted into one of the two said apertures to hook to it and hence hinder the opening of the box lid: these arrangements however suffer from the drawback that the box base can be opened by delicately deforming the closure panel firstly on one side and then on the other, to firstly uncouple one hook-shaped tooth and then the other hook-shaped tooth from their respective apertures.
In EP-B-0709293 a knurling is provided extending along the panel and along the entire width of the respective tab on the box base so that when this base is opened for the first time, the hook-shaped tooth (provided on that side of the base comprising said knurling) causes this knurling to break with consequent simultaneous detachment of a portion both of the tab and of the panel, hence making it easily visible that a part of the base is lacking, i.e. that it has already been opened for the first time. In this respect it is important to note that the traction force causing the knurling to break is applied by the hook-shaped tooth at an intermediate point of the entire said knurling, signifying that when the box is opened for the first time by pulling its base, this base outwardly raises the underlying flap, the hook-shaped tooth of which has to simultaneously break both that portion of knurling extending along the panel and that portion of knurling extending along the tab projecting from it. This operation, which is effected and completed while the hook-shaped tooth is raised and displaced from the box base pulled with two fingers by the person opening the box, is certainly not easy and can happen without the hook-shaped tooth deforming and uncoupling from the respective base aperture in which it is housed in the box.
In EP-A-1340684, along the entire folding line separating the tab from the respective panel in each base of the box, a knurling is provided which is broken (to hence totally detach the tab from the panel) when this base is opened for the first time, the breakage again being caused by the hook-shaped teeth projecting from the flaps below the base panel, with the same drawbacks as the aforesaid.